Packet Delay; Determining Bandwidth Requirements - Point Grey Flea3 GigE Technical Reference

Point Grey Flea3 GigE Technical Reference
Packet size influences the number of interrupts generated which affects CPU usage. The larger the packet size, the
fewer the interrupts for the same amount of data. To minimize CPU usage, increase the packet size.
The upper limit depends on your host adapter, your Ethernet switches (if used), and the camera.
To adjust the packet size:
From the GigE Configurator with your adapter selected, click Open Network Connections to open the Windows Adapter
Properties. Adjust the packet size of your host adapter to ~9000 (the standard jumbo packet size). If your adapter does
not support such a large packet (or MTU) size, then you will experience slightly higher CPU usage.
Packet size for the camera can be adjusted using the FlyCap demo program, the GevSCPSPacketSize GenICam
feature, or the GigE Vision Bootstrap registers
more information, consult the FlyCapture SDK Help.
Changing the packet size may impact throughput depending on the packet delay setting.
2.4.3.2

Packet Delay

The stream channel packet delay (SCPD) indicates the number of ticks (at the frequency of the Timestamp Tick
Frequency) to insert between each packet. The default packet delay is 400.
The Point Grey Timestamp Tick Frequency is normally 125,000,000 ticks/second, but can be verified by the the
GevTimestampTickFrequency GenICam feature, or the Timestamp Tick Frequency Bootstrap register
The packet delay acts like a gap between packets during transmission. This delay allows the host to process the current
packet before the arrival of the next one. When you increase the packet delay value from zero, you reduce the
effective bandwidth assigned to the camera and thereby also reduce the possibility of dropped frames.
Increasing the packet delay may require the frame rate to be reduced to meet the available maximum bandwidth.
Achieving a desired frame rate may require decreasing the packet delay.
To adjust the packet delay:
Packet delay for the camera can be adjusted using the FlyCap demo program, the GevSCPD GenICam feature
100), or the GigE Vision bootstrap registers
information, consult the FlyCapture SDK Help.
2.4.3.3

Determining Bandwidth Requirements

The maximum bandwidth available is 125 MB. This includes image data, control data and image resends, which occur
when frames are being dropped. Each image and each packet has a certain amount of overhead that will use some
bandwidth. Therefore, when calculating your bandwidth requirements, you should not attempt to use the full maximum
of 125 MB.
Revised 10/29/2013
Copyright ©2010-2013 Point Grey Research Inc.
From the GigE Configurator with your camera selected, click Discover Maximum
Packet Size. This tests the network to see the maximum size that can be sent and
received through all your network components. Set your camera's and host
adapter's packet size to be less than or equal to this maximum.
Increasing the packet delay is recommended when running multiple cameras through an Ethernet
switch.
(page
(page 109). The FlyCapture SDK also supports configuring the SCPS. For
109). The FlyCapture SDK also supports configuring the SCPD. For more
2 Flea3 GigE Installation
(page 109).
(page
13